Caption: Leishmania parasites. Coloured transmission electron micrograph (TEM) of several Leishmania sp. parasitic protozoans. Leishmania protozoans cause the tropical disease leishmaniasis, which is transmitted by bites from infected sandflies. There are two forms of the disease. Cutaneous leishmaniasis affects the skin and mucus membranes, giving rise to an ulcer at the site of the sandfly bite. This mainly heals naturally, although scarring may occur. The more serious kala-azar causes fever and liver damage, and can be fatal. Treatment is with anti-protozoal drugs.